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Question about oil pressure and when it bypasses

in 912 / 914 Technical Questions 6 years ago

  • Re: Question about oil pressure and when it bypasses

    by » 6 years ago

    I would take a step back and complete the simultaneous dual (Electrical and Mechanical) gauging exercise.
    The mechanical gauges respond instantaneously to any pressure changes.
    Electronic gauges tend to display the pressure averaged over the previous few seconds.
    - - - - -
    The Oil needs to be at 50°C (120°F) before applying full power.
    This will ensure that the Oil Pressure remains below 70psi which is the real concern.
    Pressure tends to go DOWN as the Oil thins out when the temperature goes UP.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: Question about oil pressure and when it bypasses

    by » 6 years ago

    Sorry I haven't updated lately, been working alot of overtime lately...

    I agreed with Bill and did his idea of hooking up both gauges. Sorry the video isn't better.
    https://photos.app.goo.gl/RnaH72CuP7QMJxVA6

    Did 6 takeoffs. The video shows first and last.
    Could not get either guage to drop below 45?!?!

    Got 8.7 ohms on the old sender and new 2 prong sender (Uma said it was good)
    Replaced the guage with my ohm meter and did 3 takeoffs. I crossed referenced those readings with list that Uma gave me. From that test, seems like guage is good.

    Any suggestions on what to do next?
    I still have both guages hooked up, fly some more with them?
    Put everything back to normal and fly with it dropping now and then in takeoff?

    Bill,
    I read an older post of yours, I believe it said that resonance of the motor sometimes make the oil pressure or sender jump around, think this is what it could be?

    Thank all!
      
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  • Re: Question about oil pressure and when it bypasses

    by » 6 years ago

    I will assume the FIRST Takeoff is the Second Video that starts with the Oil Pressure in the 60psi range and the Oil is cold.

    It could be the regulator bouncing around but we can't tell until it goes wacky again.
    The Key point to note will be if both gauges drift at the same time, or just one of them does.
    If they both track together, then it is a regulation problem, if only one drifts, it is an instrumentation issue.

    Right now it looks like it is working and "You can't fix it if it "Ain't" Broke!!!"

    You do not need to keep videoing it every minute, just keep an eye on it.

    P.S. I hope you are not trying to fly and video at the same time.

    Bill.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report

  • Re: Question about oil pressure and when it bypasses

    by » 6 years ago

    Thx Bill,

    Actually the higher reading is from the last takeoff.

    Guess I'll leave the mechanical guage on for a few more flights and watch it as u suggested.

    Just seems wierd that adding a "T" and another guage solved the problem...
    I do have the sender secured to the motor ground temporarily.
    Maybe the sender is seeing less vibration than when it was on the firewall or motor?
      
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  • Re: Question about oil pressure and when it bypasses

    by » 6 years ago

    Your Pressure changes are smooth but "Wonky"!!! :blink:
    I would not suspect it is the regulator just yet.

    The symptoms are more consistent with the Oil Pump Inlet hose being restricted.
    The oil Pump is capable of moving 3 liters of Oil per 1000rpm.
    In reality, it moves 2-3 gallons per minute at 5000rpm.
    This is the equivalent of a typical Garden hose except it has to move that much Oil by Suction, NOT Pressure.
    Any restriction in the Suction line is going to cause a partial Oil Starvation event at the OIl pump resulting in partial Oil Pressure.

    I would disassemble and confirm that the Oil Path is unrestricted from the pickup tube in the bottom of the Oil Tank through to the Oil Pump.
    Take it apart and run a Rifle Bore Cleaning Patch through it if you have to.
    Get Anal!!! :ohmy:
    Assume it is bad until you have confirmed that it is good.
    Something is wrong here and pretending that it isn't will not end well.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
    Report
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